Fix the tooltip for thumbnail view option in gallery on tabbing

ui/file_manager/gallery/js/gallery.js

Index: ui/file_manager/gallery/js/gallery.js
diff --git a/ui/file_manager/gallery/js/gallery.js b/ui/file_manager/gallery/js/gallery.js
index 1bbde3214667fb4923938b0c8da90762a0dce4e4..b866cbab962a8b3ce527d56f5e4d45ea9a8b729f 100644
--- a/ui/file_manager/gallery/js/gallery.js
+++ b/ui/file_manager/gallery/js/gallery.js
@@ -537,6 +537,21 @@ Gallery.prototype.onChangeToSlideMode_ = function() {
   this.changeCurrentMode_(this.slideMode_);
 };
 
+
+/**
+ * Update attributes of slide/thumbnail toggle button
+ * @param {Event=} event Event that caused this call
+ * @private
+*/

[oka, 2017/01/12 01:59:24]

Add a space before *.

[takise, 2017/01/12 04:08:05]

Done.

+

[oka, 2017/01/12 01:59:24]

Remove this empty line.

[takise, 2017/01/12 04:08:05]

Done.

+Gallery.prototype.updateModeButtonAttribute_ = function(event) {
+  var button = event.currentTarget;

[oka, 2017/01/12 01:59:24]

Are you sure that event is not undefined? If event is undefined, this line
causes error.
I guess you can use this.modeSwitchButton_ here instead.

[takise, 2017/01/12 04:08:05]

Done.

+  if (this.currentMode_ === this.slideMode_)
+    button.setAttribute("aria-label", str("GALLERY_SLIDE"));
+  else
+    button.setAttribute("aria-label", str("GALLERY_THUMBNAIL"));
+}
+
 /**
  * Change current mode.
  * @param {!(SlideMode|ThumbnailMode)} mode Target mode.
@@ -566,6 +581,8 @@ Gallery.prototype.changeCurrentMode_ = function(mode, opt_event) {
     var thumbnailRect = ImageRect.createFromBounds(
         this.thumbnailMode_.getThumbnailRect(thumbnailIndex));
 
+    this.updateModeButtonAttribute_(opt_event);

[oka, 2017/01/12 01:59:24]

I think this line should be moved to setCurrentMode_.
The comment of setCurrentMode_ reads "Sets the current mode, update the UI.". It
looks the appropriate place to update the button attribute.

[takise, 2017/01/12 04:08:05]

Done.

+
     if (mode === this.thumbnailMode_) {
       this.setCurrentMode_(this.thumbnailMode_);
       this.slideMode_.leave(